One example of a conventional match-plate molding machine is disclosed in the publication WO2005/058528 A1. The disclosed molding machine includes a pair of hydraulic cylinder systems for actuating upper and lower squeeze members, and a hydraulic power unit for energizing these hydraulic cylinder systems. The hydraulic power unit includes a piping system that supplies oil from a hydraulic pump to the pair of hydraulic cylinder systems. The piping system is typically provided with an accumulator in order to reduce the power of a motor that drives the hydraulic pump for supplying the oil, to stabilize a hydraulic circuit, to shorten the period of the cycle, and to buffer the oil.
In such a conventional machine, however, there is an inconvenience in that the minimum value of the pressure of the oil supplied to the pair of the hydraulic cylinder systems cannot be below the holding pressure of the accumulator against the oil when the squeeze members squeeze the molding sand by actuating them as the pair of the hydraulic cylinder systems are extended.
Accordingly, one purpose of the present invention is to provide a match-plate molding machine that causes the value of the oil supplied to a pair of hydraulic cylinder systems that drive a pair of squeeze members to be below the holding pressure of an accumulator against the oil.